A lot of us "outgrow" our first gear purchases because we buy what I think of as learner gear. I know I did. I wanted gear, but I wasn't sure I was going to be doing enough diving to warrant spending the money on gear that was the best for the sort of diving I was doing--and this is where TSandM's comment makes sense: if you're wanting a different sort of gear, it doesn't matter how old your original stuff is. Before long I realized I'd be doing a lot of diving, so I bought all new stuff that matched my needs better, and I gave my old stuff to my daughter, who dives infrequently and doesn't care as much about the specific functions of different elements of the gear. I've been using my current reg set for 12 years. I used a BCD for 8 years of recreational diving (with lots of use as a dive professional) before a part of it wore out that couldn't be repaired. I've just bought some brand new stuff over the past few weeks, but it's for an entirely different style of diving, so I am confident that I'll still be using the "old" stuff very frequently for quite some time. (The new stuff is sidemount equipment, and the old stuff is backmount.)
So if you haven't outgrown your equipment and you still like the functionality of it for the sort of diving you do, there's no reason for you to invest in new gear. Take that money and go diving instead!